Hello, adventuress.
Yeah, I created this Topic last year, for the Garlean Empire's invasion in Coerthas...! However, since you brought it up, and to answer your question, maybe you or other adventurers may find useful
my last journal entry, where I talk about my recent battles against these new imperial assaults.
I also put a mini-guide at the beginning and what I discovered so far on the pattern of this new event. I could try to understand it only in the past days, since the event is brand new, so if others here would like to add their experience, in case I'll edit my post with even more concrete informations.
But as it is now, it should be a fair guide to catch the event in the 3 city-states. I wonder if the Garleans will ever reach Ishgard's gates, too...
...Oh well, I'll briefly update the first post here, too, so there's everything in one post. Tomorrow I'll better fix it up, now Sleep Time.